1. Field of the Invention
The present invention relates to an organic electroluminescent element and method of manufacturing same.
2. Description of the Related Art
Organic electroluminescent elements are elements constructed using organic compounds as light-emitting materials which emit light in accordance with electrical signals.
Organic electroluminescent elements basically comprise an organic light-emitting layer interposed between a pair of opposing electrodes. Light emission is a phenomenon occurring when electrons are injected by one electrode and holes are injected by another electrode, so as to excite the light-emitting member within the light-emitting layer to a higher energy level, such that when the excited light-emitting member returns to its original lower energy state, the surplus energy is released as light.
A hole injection layer for the electrode which injects holes, and an electron transporting layer is provided for the electrode which injects electrons in addition to the aforesaid basic construction so as to increase the luminous efficiency.
An example of organic electroluminescent elements using a single crystal anthracene as a light emitter is disclosed in U.S. Pat. No. 3,530,325.
Japanese Laid-Open Patent Application No. SHO 59-194393 discloses an organic electroluminescent element comprising a combination of an organic light-emitting layer and a hole injecting layer.
Japanese Laid-Open Patent Application No. SHO 63-295695 discloses an organic electroluminescent element comprising a combination of an organic material electron injecting/transporting layer and an organic material hole injecting/transporting layer.
These multi-layer construction organic electroluminescent elements are formed of multiple layers of organic luminescent material, charge-transporting organic material (charge-transporting member), and electrodes, and accomplish light emission by the injection of holes and electrons by the respective electrodes which move within the charge-transporting member, and recombine. Examples of useful organic luminescent material includes organic colorants which luminesce such as 8-quinolinol-aluminum complex, coumarin compound and the like. Examples of useful charge-transporting materials include N,N′-di(m-tolyl)N,N′-diphenylbenzidene, 1,1-bis[N,N-di(p-tolyl)aminophenyl]cyclohexane and like diamino compounds, 4-(N,N-diphenyl)aminobenzaldehyde-N,N-diphenylhydrozone compound and the like. Porphyrin compounds such as copper phthalocyanine have also been proposed.
Although organic electroluminescent elements have high luminescence characteristics, they have inadequate storage stability and stability when luminescing and are as yet unsuitable for practical use.
Japanese Laid-Open Patent Application No. HEI 7-142168 discloses an example of an improvement of the aforesaid organic electroluminescent elements by subjecting the positive electrode to plasma surface processing, and subsequently forming an organic layer on said positive electrode without exposing the electrode to air.
Japanese Laid-Open Patent Application No. HEI 7-220873 discloses a dry etching process as a method of plasma surface processing of a positive electrode, but did not disclose all details of this dry etching process.